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Cambridge International Examinations
Cambridge International Advanced Subsidiary and Advanced Level
* 0 3 2 4 7 2 3 3 5 5 *
9700/21
BIOLOGY
Paper 2 Structured Questions AS
May/June 2016
1 hour 15 minutes
Candidates answer on the Question Paper.
No Additional Materials are required.
READ THESE INSTRUCTIONS FIRST
Write your Centre number, candidate number and name on all the work you hand in.
Write in dark blue or black pen.
You may use an HB pencil for any diagrams or graphs.
Do not use staples, paper clips, glue or correction fluid.
DO NOT WRITE IN ANY BARCODES.
Answer all questions.
Electronic calculators may be used.
You may lose marks if you do not show your working or if you do not use appropriate units.
At the end of the examination, fasten all your work securely together.
The number of marks is given in brackets [ ] at the end of each question or part question.
This document consists of 13 printed pages and 3 blank pages.
DC (ST/FD) 109211/4
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2
Answer all the questions.
1
Table 1.1 shows features of three infectious diseases: malaria, tuberculosis (TB) and cholera.
Complete Table 1.1.
Table 1.1
feature
malaria
tuberculosis
name of pathogen
………………….....…
falciparum
cholera
Mycobacterium
tuberculosis
………………….....…
………………….....…
type of organism
method of
transmission
………………….....…
bacterium
………………….....…
………………….....…
………………….....…
………………….....…
………………….....…
………………….....…
………………….....…
drinking water and
food contaminated
with human faeces
[6]
[Total: 6]
2
Macrophages synthesise intracellular enzymes.
Fig. 2.1 is a summary diagram of events that occur in a macrophage.
bacteria
$
%
&
+
'
*
)
(
Fig. 2.1
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(a) (i)
Name the process at A.
.......................................................................................................................................[1]
(ii)
Name the stages of protein synthesis that occur at E and at F.
E ........................................................................................................................................
F ....................................................................................................................................[2]
(iii)
Name organelles B, G, H and J.
B ........................................................................................................................................
G .......................................................................................................................................
H ........................................................................................................................................
J ....................................................................................................................................[4]
(b) Describe what happens to the bacteria between C and D.
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...............................................................................................................................................[3]
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(c) Macrophages are antigen presenting cells (APCs). Antigens from pathogens such as the
bacteria shown in Fig. 2.1 are presented to helper T-lymphocytes as shown in Fig. 2.2.
helper
T-lymphocyte
antigen
APC
T cell receptor
Fig. 2.2
Very few helper T-lymphocytes respond to the presence of APCs by binding in the way shown
in Fig. 2.2.
Suggest why this is so.
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[Total: 12]
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3
A student studied a transverse section of the trachea of a small mammal. The student drew a plan
diagram of the section as shown in Fig. 3.1.
0
Fig. 3.1
Fig. 3.2 is a photomicrograph of the area labelled M in Fig. 3.1.
1
2
3
VPRRWK
PXVFOH
Fig. 3.2
(a) Name:
(i)
the type of epithelium at N
.......................................................................................................................................[1]
(ii)
the structures at O
.......................................................................................................................................[1]
(iii)
the tissue at P.
.......................................................................................................................................[1]
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(b) Smooth muscle in the trachea and in the bronchi relaxes during strenuous exercise.
Suggest the advantages of relaxing this smooth muscle during periods of strenuous exercise.
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(c) The walls of the trachea and bronchi contain elastic fibres.
Elastic fibres are made of bundles of the fibrous protein elastin.
•
•
•
•
•
•
Each molecule of elastin is a single polypeptide.
The primary structure contains a large proportion of the amino acid glycine.
Glycine has a hydrophobic R group.
Glycine does not occur at regular intervals in the polypeptide.
The polypeptide forms random coils that change shape as the elastic fibres are stretched
and recoil.
Elastin molecules are joined to each other by many covalent bonds to form a
cross-linked network.
Describe two ways in which the structure of a collagen molecule differs from the structure of
an elastin molecule described above.
1 ................................................................................................................................................
...................................................................................................................................................
2 ................................................................................................................................................
...............................................................................................................................................[2]
[Total: 7]
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4
(a) Transpiration is often described as ‘an inevitable consequence of gas exchange in leaves’.
Explain what is meant by this description.
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(b) Explain how hydrogen bonding is involved in the movement of water in the xylem.
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Southern beech trees of the genus Nothofagus grow in forests in the South Island of New Zealand.
Fig. 4.1 shows a small part of a forest.
Most of the trees in the forests form a thick canopy of leaves. These are known as canopy trees.
The tallest trees are known as emergent trees. Some trees do not reach the canopy and are
known as suppressed trees.
canopy
trees
emergent tree
suppressed
tree
Fig. 4.1
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Researchers determined the rates of transpiration of emergent, canopy and suppressed trees in
a forest over a 14 hour period from 06.00 until 20.00 on one day in the summer. The results are
shown in Fig. 4.2A. They also recorded changes in light intensity above the canopy over the same
time period as shown in Fig. 4.2B.
10
$
9
8
Key
emergent trees
7
mean
transpiration
rate per tree
/ kg h–1
6
canopy trees
suppressed trees
5
4
3
2
1
0
06.00
08.00
10.00
12.00
14.00
time of day
16.00
18.00
20.00
2.0
%
1.5
light intensity
/ arbitrary units 1.0
0.5
0.0
06.00
08.00
10.00
12.00
14.00
time of day
Fig. 4.2
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18.00
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(c) Use Fig. 4.2A to compare the transpiration rates of the emergent, canopy and suppressed
trees in the forest over 14 hours.
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(d) The factors that affect transpiration rate vary considerably at different places inside forests.
Use the information in Fig. 4.1 and Fig. 4.2 to suggest reasons for the difference in the
transpiration rates of the emergent and suppressed trees.
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[Total: 14]
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5
(a) Fig. 5.1 is a diagram of part of an animal cell in a stage of mitosis.
spindle fibres
Fig. 5.1
(i)
Draw a diagram in the space below to show the stage of mitosis that follows the stage in
Fig. 5.1.
[3]
(ii)
Describe the roles of the spindle fibres during mitosis.
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Bone marrow contains many stem cells. Some of these stem cells are responsible for the
replacement of red blood cells.
During the production of red blood cells a series of changes occur to the cell structure.
Fig. 5.2 shows the production of a red blood cell from one of these stem cells.
stem cell
cell <
many
mitotic
divisions
many
mitotic
divisions
cell ;
final changes
in cell
structure
mature red
blood cell
Fig. 5.2
(b) (i)
Outline the changes that occur as cell X becomes a mature red blood cell.
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(ii)
Suggest what may happen to cell Y.
.......................................................................................................................................[1]
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(c) People who travel to high altitude become acclimatised to the conditions.
Athletes often train at high altitude before competing at sea level.
A group of male and female athletes who trained at sea level moved to high altitude for further
training. Sports scientists analysed blood samples taken from the athletes to measure any
changes in the concentration of haemoglobin in the blood and changes in the haematocrit.
Haematocrit is the volume of red blood cells expressed as a percentage of the total volume of
a sample of blood.
The results are shown in Table 5.1.
Table 5.1
at sea level
after 19 days at
high altitude
mean concentration of
haemoglobin in the blood
/ g 100 cm–3
13.3
15.1
mean haematocrit
41.0
42.5
feature of the blood
percentage
increase
.....................
3.7
(i)
Complete Table 5.1 by calculating the percentage increase in haemoglobin concentration.
[1]
(ii)
Explain why it is necessary for the athletes to increase the concentration of haemoglobin
in their blood when acclimatising to high altitude.
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[Total: 14]
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6
Fig. 6.1 shows an incomplete diagram of the fluid mosaic model of membrane structure. The
diagram shows the cell surface membrane of a eukaryotic cell.
Fig. 6.1
(a) State what is meant by the term fluid mosaic.
...................................................................................................................................................
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...............................................................................................................................................[2]
(b) State the thickness of a cell surface membrane.
...............................................................................................................................................[1]
(c) List four features of cell surface membranes of eukaryotic cells that are not visible in Fig. 6.1.
1 ................................................................................................................................................
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2 ................................................................................................................................................
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3 ................................................................................................................................................
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4 ................................................................................................................................................
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[Total: 7]
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